1. Field of the Invention
The invention is related to the detection of errors in digital computing systems, and more particularly to the detection of errors in a number of stations which are interconnected by a bus that carries address and data to a processor or sequencer and the stations. The stations may be independent sequencers or processors, or they may be gate arrays each of which have a specified function which is called into operation by signals from the processor or sequencer.
It is common to employ "handshake" signals between a processor or sequencer and operating stations, such as gate arrays, to control the exchange of data and address signals. The detection of errors that occur in large scale processing systems which employ handshake to changes and which have a number of stations is critical in order to avert damage to system components, especially to expensive circuit elements and gate arrays which could fail due to hardware failures in other areas. The system employs a tri-state bus driver. Tri-state buses and bus drivers are well known. U.S. Pat. No. 5,212,800, issued May 18, 1993 in the name of William D. Mensch, Jr., entitled "Method and Apparatus for Sensing Trinary Logic States in a Microcomputer Using Bus Holding Circuits," and U.S. Pat. No. 5,210,449, issued May 11, 1993 in the names of Kiyoshi Nishino, et al., entitled "Edge-Triggered Tri-State Output Buffer," show examples of such types of devices. A tri-state bus has two logic states and a third state which is a high impedance state. When the bus is set into its third state, it protects components from failed components and from also failing.